Primary infection with varicella-zoster virus (VZV) causes chickenpox, and reactivation of the virus from latency results in zoster. The goals of this project are to identify and determine the function of VZV genes that are expressed during latency and to develop new animal models to study acute and latent infection. Two chimpanzees inoculated with VZV developed a papular rash ten days after inoculation. VZV DNA was detected in white blood cells of both animals shortly after inoculation and in a skin biopsy from one of the animals at the time of the rash. Additional experiments are underway to study a VZV gene (ORF21) that has been reported to be expressed during latency in animals. The regulation of VZV ORF21 gene expression will be analyzed and expression of this gene in animal models and in humans will be studied.